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Onland-Moret NC van der A DL van der Schouw YT Buschers W Elias SG van Gils CH Koerselman J Roest M Grobbee DE Peeters PH 《Journal of clinical epidemiology》2007,60(4):350-355
OBJECTIVE: The case-cohort design combines the advantages of a prospective cohort study and the efficiency of a case-control design. Usually a Cox proportional-hazards model is used for the analyses. However, adaptation of the model is necessary because of the sampling. We compared three methods that were proposed in the literature, which differ in weighting of study subjects: Prentice's, Barlow's, and Self and Prentice's method. STUDY DESIGN AND SETTING: In a cohort of 17,357 women we studied the relationship between body mass index and cardiovascular disease (n=821) with varying subcohort sizes (sampling fraction=0.005, 0.01, 0.05, 0.10, 0.15). RESULTS: Even with a sampling fraction of 0.01, all three methods showed identical estimates and standard errors (SE). With sampling fractions >or=0.10, results of the case-cohort analyses were similar to the full-cohort analyses. With simulations, the three methods provided different results if the full cohort is small (<1,250 subjects, subcohort=10%, 8% failures) or if the subcohort size was smaller than 15% (full cohort of 1,000 observations, 8% failures). The difference between the methods did not change with the number of failures or with different effect sizes. CONCLUSION: In the above-mentioned situations, the effect estimates and SE of Prentice's method most resembled the estimates of the full-cohort estimates. 相似文献
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A portable target controlled infusion system for propofol has been developed based on a Psion hand-held microcomputer and the Ohmeda 9000 syringe pump. The system uses a pharmacokinetic model which describes the distribution and elimination of propofol to achieve and maintain any selected target blood concentration. Target blood concentrations of 1 g/ml, 3 g/ml and 5 g/ml were selected in laboratory trials and the cumulative volumes delivered by the Psion system each minute were compared with the theoretical output calculated by the pharmacokinetic model. The results obtained showed that the computer system delivered volumes which were always within 2% of the theoretical values. This system offers a convenient and simple method of maintaining anaesthesia using propofol. 相似文献
106.
NC Molony BSc FRCS D Santana-Hernandez DLO LMS PJ Wardrop FRCS M Armstrong FRCS SJ Moralee FRCS 《International journal of clinical practice》1998,52(6):372-373
SUMMARY Anecdotal evidence from several ENT departments suggests that pain following tonsillectomy is worst on the second and/or third days after surgery. This study tests this hypothesis. A pilot study with 19 subjects suggested this theory might well be true. A fuller study was then carried out on 91 subjects with standardised surgical and anaesthetic techniques, and standardised analgesia for five days postoperatively. Pain on the second and third postoperative days was compared with that eight hours after the operation and on the first, fourth and fifth postoperative days. No statistically significant difference was found. There is increasing pressure for early discharge from hospital after surgery. If pain following tonsillectomy is not going to become worse at home, this will tend to make early discharge more acceptable to patients. 相似文献
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Martha J Foxall PhD RN Lani Zimmerman PhD RN Roberta Standley MSN RN Barbara Bene Captain USAF NC MSN RN 《Journal of advanced nursing》1990,15(5):577-584
This study compared the frequency and sources of nursing job stress perceived by 35 intensive care (ICU), 30 hospice and 73 medical-surgical nurses. Analysis of variance revealed no significant differences among the three groups of nurses on the overall frequency of job stress. Post-hoc Tukey tests demonstrated a significant difference in three stress subscales among the three groups. ICU and hospice nurses perceived significantly more stress than medical-surgical nurses related to death and dying; ICU and medical-surgical nurses perceived significantly more stress than hospice nurses related to floating; and medical-surgical nurses perceived significantly more stress than ICU and hospice nurses related to work-overload/staffing. Spearman-Rank Correlation revealed no significant correlations among the three groups in their rank-ordering of the eight stress subscales. Death and dying situations were the most stressful to ICU and hospice nurses, while work-overload/staffing situations were the most stressful to medical-surgical nurses. Results of the study, although not generalizable, have implications for nurse managers. 相似文献
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Controversy exists about the suitability of blood from autologous donors for homologous use. We compared the infectious disease test results of 426 autologous donors, designated by donor history as suitable for homologous use, to those of 86,138 volunteer donations collected over the same 5 month period. Although donor characteristics differed, the relative risk of a positive test for anti-HBc in the autologous group was 2.09. When 413 autologous donors were compared to 413 volunteer donors matched for age, sex, and zip code, the relative risk of a positive test for anti-HBc in the autologous group was 3.2. If anti-HBc is a marker for non-A, non-B hepatitis transmissibility, then our autologous group is not as safe as our volunteer donors. We recommend that autologous blood, even when designated by donor history and laboratory screening results as suitable for homologous transfusion, not be used for other than the intended autologous recipient. 相似文献
109.
SUMMARY Drugs affecting the leukotriene pathway are emerging as a new class of asthma treatment — the first for more than 20 years. Development of these leukotriene antagonists should lead to greater understanding of the underlying processes in asthma and may result in a safe, oral, anti-asthmatic drug to benefit particular groups of asthmatic patients. 相似文献
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